Patterning non-planar surfaces

ABSTRACT

A pattern is formed on a non-planar surface by forming a layer of photoresist on a part having a surface comprising a non-planar surface area. A deformable mask is aligned over at least a portion of the non-planar surface area of the part such that the deformable mask substantially deforms in a manner corresponding to at least a portion of the non-planar surface area of the part. The photoresist on the part is exposed through the mask so as to transfer a desired pattern onto the part while the deformable mask is maintained in a deformed state.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/822,216, filed Aug. 11, 2006, entitled“PATTERNING NON-PLANAR SURFACES”, the disclosure of which is herebyincorporated by reference. This application also claims the benefit ofU.S. Provisional Application Ser. No. 60/822,134 filed Aug. 11, 2006,entitled “PATTERNING COMPOSITIONS, MASKS AND METHODS” the disclosure ofwhich is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates in general to contact lithographytechniques and, more particularly, to contact lithography systems andmethods that utilize deformable masks for patterning non-planarsurfaces.

In conventional contact photolithography, a substrate having a flat orflattened surface is coated with a photoresist material. A flat glassmask is then aligned over the photoresist material and is brought intointimate contact with the substrate. The flat mask includes a maskpattern defined by areas of the mask that are opaque to light emitted byan ultra violet (UV) lamp or other suitable exposure source, and areasof the mask that are transparent to light from the UV lamp. An exposureoperation is then performed whereby the photoresist material on thesubstrate is selectively exposed to light from the UV lamp through theflat glass mask. In particular, the light emitted by the UV lamptransmits through the transparent portions of the mask and penetratesthe photoresist material below. The photoresist material isphotosensitive to the light, thereby altering the chemical resistance ofthose exposed regions of the photoresist material to a correspondingdeveloper. The changed resistance regions of the photoresist materialare referred to herein as the exposed regions. The areas of the maskthat are opaque block the light from the UV lamp from altering thoseregions of the photoresist material corresponding to the opaque areas ofthe mask, thus defining unexposed regions of photoresist material.

A subsequent developing process is then performed, whereby the developeris used to remove either the exposed regions or the unexposed regions ofphotoresist material from the substrate, resulting in a pattern in theremaining photoresist material corresponding to the pattern on the mask.In this regard, the corresponding pattern may be a positive or negativeimage of the mask pattern, depending upon whether the developing processremoves the exposed or unexposed regions of the photoresist material.Once the pattern is prepared in the photoresist material, any number ofconventional processes may be carried out. For example, subsequentdeposition or etching processes may be performed as the specificapplication requires.

Photosensitive compounds are capable of producing patterns having arelatively fine feature size. However, as the desired feature size getssmaller, it becomes increasingly important for intimate contact to bemade between the photomask and the substrate. For example, at the edgesof the pattern, light is scattered and diffracted. Accordingly, ifsufficiently intimate contact between the photomask and the photoresistmaterial is not achieved, then it is possible for regions of thephotoresist that are intended to be unexposed, e.g., regions of thephotoresist that are proximate to the opaque edges of the pattern, tounintentionally become exposed, thus resulting in an inaccurate transferof the pattern from the mask to the substrate.

There are an increasing number of applications where it is desirable topattern non-planar surfaces. For example, many frequency selectivesurfaces such as those found on radomes, windows, the receiving surfacesof RF antennas, etc., are non-planar surfaces that may require amicromesh or other suitable pattern applied thereto. However, anycurvature in the surface complicates the patterning process and makesthe achievement of precise patterns difficult. Moreover, a flat glassmask may not be capable of projecting a useful image onto a non-planarsubstrate. For example, as the resolution and size of the lines in thepattern are reduced, it may become extremely difficult to use a flatmask due to the distortion introduced from a lack of intimate contactbetween the mask and the non-planar portion of the correspondingsubstrate that is to be patterned.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a method of forming apattern on part comprises forming a layer of photoresist on a parthaving a surface comprising a complex non-planar surface area andpositioning the part within a chamber defined by a chamber base and apressure vessel such that the part is positioned within the chamberbase, wherein a first pressure source is coupled to the chamber base anda second pressure source is coupled to the pressure vessel. The methodfurther comprises securing a deformable mask in a retaining devicebetween the chamber base and the pressure vessel so as to align thedeformable mask towards the photoresist on the part and divide thechamber into a pressure vessel space above the mask and a chamber basespace below the mask, drawing a first vacuum in the chamber base spaceusing the first pressure source, applying a positive pressure in thepressure vessel space using the second pressure source to deform themask to correspond substantially to the part including the complexnon-planar surface area and exposing the photoresist on the part throughthe mask after the mask deforms to correspond to the part including thecomplex non-planar surface area. The method still further comprisesremoving the part from the chamber and developing the photoresist on thepart.

According to another aspect of the present invention, a method offorming a pattern on a non-planar surface of a part comprises deforminga mask against a mold, bringing the mask into cooperation with a part tobe patterned while the mask is deformed against the mold, wherein thepart has at least one non-planar surface area coated with a photoresistlayer and pulling a vacuum between the mask and the part such that themask deforms to the part including the at least one non-planar surfacearea. The method further comprises removing the mold from the mask sothat the mask remains deformed to the part, exposing the part throughthe mask and developing the part.

According to yet another aspect of the present invention, a method ofmaking a deformable mask for contact lithography comprises applyingphotoresist over a deformable mask substrate and shaping the masksubstrate to a first predetermined shape by wrapping the mask substrateabout a frame. The method further comprises applying a master havingdesired artwork thereon over the photoresist on the deformable masksubstrate, exposing the photoresist using an exposure source to define adesired pattern while the deformable mask is in the first predeterminedshape and forming the pattern in the photoresist by removing portions ofthe photoresist corresponding to a desired pattern, wherein thedeformable mask does not retain a shape corresponding to a part having anon-planar surface area to be patterned by the deformable mask.

According to yet a further aspect of the present invention, a system forforming a pattern on a non-planar surface of a part comprises a chamberbase, a pressure vessel and a retaining device that is positionablebetween the chamber base and the pressure vessel to secure a deformablemask therebetween, wherein a chamber is defined in the inside spacedefined by the chamber base and the pressure vessel. The system furthercomprises a first pressure source coupled to the chamber base operableto provide a negative pressure within the chamber to draw the masktowards a part installed within the chamber base, a second pressuresource coupled to the pressure vessel to provide a positive pressurewithin the pressure vessel to direct the mask towards the part so thatthe mask corresponds to at least one non-planar surface of the part anda third pressure source coupled to the pressure vessel to provide anegative pressure within pressure vessel, e.g., to promote adjustment ofthe mask relative to the part, wherein an exposure source is utilized toexpose the part through the mask while the mask is in a deformed state.

According to yet a further aspect of the present invention, a system forforming a pattern on a non-planar surface of a part comprises a chamberbase for holding a part having at least one non-planar surface area tobe patterned, a pressure vessel that detachably connects to the chamberbase and a retaining device between the chamber base and the pressurevessel to secure a deformable mask therebetween, wherein a chamber isdefined in the inside space defined by the chamber base and the pressurevessel. The system further comprises at least one of a mold or a backingdevice within the pressure vessel corresponding to a desired shape todeform the mask before engaging the mask with the part, a first pressuresource coupled to the chamber base operable to provide a pressure withinthe chamber in the chamber base to draw the mask towards a partinstalled within the chamber base and a second pressure source coupledto the pressure vessel to provide a pressure within the pressure vesselto deform the mask in cooperation with the mold or backing device.

According to yet another aspect of the present invention, a method ofpatterning a part comprises preparing a part having areas transmissiveto an exposure source and areas that are not transmissive to theexposure source to define a desired mask pattern. The method furthercomprises coating the part with a layer of photoresist, exposing thephotoresist through the part and developing the photoresist afterexposure to the exposure source.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following detailed description is best understood when read inconjunction with the following drawings, where like structure isindicated with like reference numerals, and in which:

FIG. 1 is a schematic block diagram of system for applying a deformablemask to a curved surface for contact lithography;

FIG. 2 is a flow chart illustrating a method of creating a deformablemask for performing contact lithography on a substrate having anon-planar surface;

FIGS. 3A-3D are schematic diagrams of a system for performing an indexedexposure, showing by way of example, the indexed exposure of a photomaskwrapped around a cylinder;

FIG. 4 is a schematic diagram of a system for performing an indexedexposure;

FIG. 5 is a flow chart illustrating a method of patterning a part havinga non-planar surface;

FIG. 6 is a schematic block diagram of the system of FIG. 1 duringoperation wherein a differential pressure is used to deform the maskcorresponding to the shape of a part to be patterned;

FIG. 7 is a flow chart illustrating an exemplary approach for patterninga part having a non-planar surface area;

FIG. 8 is an apparatus for patterning a part according to the flow chartof FIG. 8, wherein the apparatus is in a first state;

FIG. 9 is the apparatus for patterning a part according to the flowchart of FIG. 8, wherein the apparatus is in a second state;

FIG. 10 is a schematic diagram of a system for performing an exposure ona part having a non-planar surface;

FIG. 11 is a schematic diagram of a system for performing an exposure ona part having a non-planar surface;

FIG. 12 is a schematic diagram of an exemplary system for shaping amask;

FIG. 13 is a schematic diagram of another exemplary system for shaping amask;

FIG. 14 is a schematic illustration of an exemplary approach where thepart to be patterned is used as the mask for an exposure operation.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the illustrated embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, specific embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand that changes may be made without departing from the spirit and scopeof various embodiments of the present invention.

General System Overview

Referring now to the drawings, and particularly to FIG. 1, a system 10is illustrated in schematic block diagram form, which is suitable forperforming contact lithography on parts having non-planar surfaces. Asshown, the system 10 defines a chamber having a first chamber component,also referred to herein as the chamber base 12 and a second chambercomponent, also referred to herein as a pressure vessel 14. The system10 further comprises a retaining device 16, a platform 18 and at leasttwo pressure sources, which are designated generally by the referencenumeral 20. As shown, the system 10 comprises a first pressure source20A coupled to the chamber base 12, a second pressure source 20B coupledto the pressure vessel 14 and a third pressure source 20C, which is alsocoupled to the pressure vessel 14.

In use, a part 24 comprising a non-planar surface area 24A is placed onthe platform 18. As illustrated, the non-planar surface area 24A is adimple that recesses into the part 24. However, in practice, thenon-planar surface area 24A can be any surface of the part 24 that isnon-planar, e.g., stepped, curved, complex including complexly curved,or having any other contour(s). As used herein, a complex non-planarsurface area differs from a simple non-planar surface area in that acomplex area has multiple changes such as relatively steep contourchanges, abrupt or otherwise sharp angles, steps, dimples, recessesand/or other features that is not merely a simple curvature. As afurther example, complex curvature differs from a simple curvature inthat a complex curvature comprises at least one change in the center ofcurvature in the non-planar surface area 24A of the part 24.

A deformable mask 26 is secured in the retaining device 16. Theretaining device 16 comprises any suitable structure for holding themask 26, and may pre-stretch or otherwise alter the shape of the mask 26from a default state. The retaining device 16 may also allow adjustmentsto be made to the positioning of the mask 26, e.g., to perform suitablealignment procedures. In its default state before use, the mask 26 isgenerally not conformal to the part 24. However, as will be describedmore fully herein, the mask 26 need not be flat.

Prior to an exposure operation, the pressure sources 20 may be operatedso as to work together, e.g., to provide a differential pressure or tooperate in sequence, to deform the mask 26 in a manner corresponding tothe part 24, including the non-planar surface area 24A, which may becomplexly shaped. Once the mask 26 has satisfactorily deformedcorresponding to the contour(s) of the part 24, an exposure operation isperformed, e.g., by positioning an exposure source 27 such as anultraviolet (UV) exposure lamp over the vessel 14, by moving the system10 under a suitable UV exposure lamp or by otherwise positioning anexposure source 27 so as to expose the part 24 through the mask 26.Regardless of the approach utilized to bring the exposure source 27 intocooperation with the system 10, an exposure occurs while the mask 26 ismaintained in a deformed state corresponding to the part 24 as will bedescribed in greater detail below.

In an exemplary implementation of the system 10, the chamber base 12comprises a stainless steel vacuum chamber that supports the retainingdevice 16 and the platform 18. The pressure vessel 14 may comprise atleast a portion 14A that is transmissive to light from the exposuresource 27. For example, the portion 14A of the pressure vessel 14 maycomprise a quartz window. Alternatively, the portion 14A of the pressurevessel 14 may comprise acrylic or other material that is sufficientlytransparent to the exposure source 27, e.g., a suitable UV lamp. As yeta further example, it may be possible to remove the pressure vessel 14and maintain the mask 26 in a sufficiently deformed position to performthe exposure operation without requiring the exposure source 27 topenetrate the pressure vessel 14, an example of which will be describedin greater detail herein. In a system configuration where the pressurevessel 14 is removed for the exposure operation, there may be no need toinclude a portion 14A that is transmissive to the exposure source 27.

In contact lithography, intimate contact of the mask 26 to the part 24becomes increasingly important as feature size decreases. As such, thedesired feature size, the size of the part 24, the specific contours ofthe non-planar surface area 24A, the pliability of the mask 26, thespecific construction of the chamber base 12, vessel 14, retainingdevice 16 and similar considerations may determine the selection of thepressure sources 20. Such considerations may include, for example,whether each pressure source is a positive pressure source, such asnitrogen, or a negative pressure source, such as a vacuum pump. Othersuch considerations may comprise the particular number of pressuressources 20 coupled to the system 10, and whether each pressure source 20couples to the chamber base 12 or the pressure vessel 14.

As used herein, the term “positive pressure” refers to a “pushing”pressure, i.e., a force acting on a surface. For example, when the mask26 is held by the retaining device 16 and the pressure vessel 14 andretaining device 16 are assembled to the chamber base 12, the mask 26defines a surface that divides a pressure vessel space above the mask 26from a chamber base space below the mask 26. In this context, a positivepressure source, such as nitrogen, can be used within the pressurevessel 14 to urge, i.e., push, the mask 26 towards a part to bepatterned in the chamber base so as to assist in deforming the mask 26to correspond to the part 24.

The term “negative pressure” is used herein to refer to a relativepressure, such as a pressure that exerts a force (relatively) less thana different force applied to the opposite side of a correspondingsurface. For example, when the mask 26 is held by the retaining device16 and the pressure vessel 14 and retaining device 16 are assembled tothe chamber base 12 as described above, if a vacuum is drawn in thechamber base space below the mask 26, the force on the mask 26 in thechamber base space is less than (and thus may be considered negativewith respect to) the force applied to the mask 26 in the pressure vesselspace. In this example, it may appear that the mask 26 is being “pulled”towards the chamber base space rather than pushed from the pressurevessel space. As such, this pressure difference may be conceptualized asa negative pressure.

Thus, for purposes of discussion herein, the term “positive pressure”may refer to a pressure that exerts a force greater than the ambientpressure inside the chamber when the mask 26 is held by the retainingdevice 16 and the pressure vessel 14 and retaining device 16 areassembled to the chamber base 12, e.g., atmosphere or some othersuitable pressure. Correspondingly, the term “negative pressure” mayrefer to a pressure that exerts a force less than the ambient pressureinside the chamber when the mask 26 is held by the retaining device 16and the pressure vessel 14 and retaining device 16 are assembled to thechamber base 12.

Still further considerations for selecting the type and/or quantity ofpressure sources 20 may include the manner and method in which thepressure sources 20 are operated. For example, the various pressuresources 20 may be utilized in cooperation with each other to perform thenecessary exposure operations. In this regard, the pressure sources 20may be used alone or in combination, and in any sequence. Thus, at anygiven time during processing, no pressure sources 20 may be in use, onlya single pressure source 20 may be in use, or multiple pressure sources20 may be simultaneously in use. Some examples of the manner of usingmultiple pressure sources 20 will be provided in greater detail herein.

In the exemplary system 10, the first, second and third pressure sources20A, 20B, 20C comprise a combination of positive and negative sources ofpressure that are configured such that a difference in pressure can beestablished within the volume of the chamber base 12 and the pressurevessel 14. In one exemplary arrangement of the system 10, the firstpressure source 20A comprises a vacuum source that is coupled to thechamber base 12 by a suitable first passageway 28. A first passagewaycontrol valve 30 is provided for controlling the vacuum applied withinthe chamber base 12. A first relief control valve 32 may also beprovided to direct the pressure from the chamber base 12 to a firstrelief passageway 34. The first relief passageway 34 allows the pressurein the chamber to be exhausted, e.g., to atmosphere via the chamber base12, first passageway 28 and the first relief passageway 34.

The second pressure source 20B comprises a positive pressure source,such as a compressed gas, e.g., nitrogen, which is coupled to thepressure vessel 14 by a suitable second passageway 36 and a vesselcommon passageway 38. A second passageway control valve 40 is providedfor controlling the pressure applied within the pressure vessel 14 viathe second pressure source 20B. The third pressure source 20C comprisesa vacuum source that is coupled to the pressure vessel 14 via a thirdpassageway 42 and the vessel common passageway 38. A third passagewaycontrol valve 44 is provided for controlling the pressure applied to thepressure vessel 14 via the third pressure source 20C. A second reliefcontrol valve 46 may also be provided to direct pressure in the pressurevessel 14 to a second relief passageway 48. The second relief passageway48 allows pressure in the chamber to be relieved, e.g., to atmospherevia the pressure vessel 14, the vessel common passageway 38 and thesecond relief passageway 48. In practice, various combinations ofvalves, ports, passageways and other control arrangements may beprovided to selectively apply, control and exhaust the first, second andthird pressure sources 20A, 20B, 20C to and from the chamber, includingthe chamber base 12 and the pressure vessel 14.

As illustrated by the exemplary part 24, the non-planar surface area 24Acomprises a relatively deep dimple that includes sharp changes of thesurface contour of the part 24 along the perimeter of the dimple.Moreover, the curvature of the dimple extends relatively far down intothe part 24. To pattern the surface of the part 24, including patterningwithin the non-planar surface area 24A, a previously patterned mask 26is secured within the retaining device 16 and is positioned over thepart 24 to be patterned. Although the mask 26 is shown as beingsubstantially flat in its initial state, other arrangements can be used,including the application of some degree of pre-chamber shaping of themask 26, such as by using a backing device or mold as will be describedin greater detail herein.

Once the mask 26 is secured within the retaining device 16 and isproperly placed, the pressure sources 20 are applied, alone or incombination and in any appropriate sequence, as the specific applicationrequires. Examples of controlling the pressure sources 20 will bedescribed in greater detail below. The pressure sources 20 deform themask 26 to correspond to the part 24. In this regard, the mask 26 maydeform without significantly corrupting the integrity of the pattern onthe mask 26, e.g., without causing breaks in the pattern or tearing ofthe mask substrate, etc., as will be described in greater detail herein.

The Mask

The mask 26 utilized with the system 10 is constructed so as to bedeformable, at least to some degree. The amount of tolerable deformationof the mask 26 will depend upon factors such as the size of the mask 26,properties of the material selected for the substrate of the mask 26,the particular geometry of the desired pattern on the mask 26 and theproperties of the material of the opaque layer of the mask 26. Forexample, the mask 26 may be either elastic or inelastic depending uponthe particular application. That is, in some applications, it may besufficient for the mask 26 to bend or flex to conform to the part 24,without stretching the substrate of the mask 26. Moreover, the mask 26may be constructed for a one-time use, or it may be possible to reusethe mask 26 depending upon a number of factors, including the processingconditions, as is discussed in greater detail below.

With reference to FIG. 2, an exemplary method 100 is illustrated forcreating a mask 26. The mask substrate is prepared at 102. Thepreparation required to construct a mask 26 will depend largely upon thematerials selected for the mask 26. For example, the mask 26 maycomprise a polymer. As such, an opaque coating, e.g., a metal, paint,varnish or other coating may need to be applied to a surface of thepolymer. In one exemplary application, the mask substrate comprises aMylar film. Thus, the preparation at 102 may comprise an optionalprocess to aluminize the Mylar. Other preparation at 102 may comprisesizing the Mylar, cleaning or otherwise preparing the surface of theMylar (or other material) to act as a suitable mask, etc.

Photoresist is applied to the mask 26 at 104. The photoresist may beapplied using any appropriate method, such as spin-coating or spraycoating. For example, an aluminized Mylar substrate may be attached to aplate of glass such that the aluminum coated side is opposite the glassplate surface, i.e., facing out, and a spin-coat method may be used tocoat the aluminum side of the aluminized Mylar substrate while the mask26 is held by the plate of glass. Other techniques for applying thephotoresist may alternatively be used. Also, a bake operation may beperformed immediately after the application of photoresist (soft bake)to remove residual solvents from the photoresist.

The mask is patterned at 106. For example, if the aluminized Mylar isprovided as a substantially flat sheet, the desired pattern may betransferred from a standard glass photomask master to the photoresistover the aluminum side of the aluminized Mylar substrate. The glassphotomask master may be held tightly against the photoresist on thesubstrate using any suitable method, such as by using a vacuum. As anexample, the edges of the flat glass photomask master may be sealed, anda needle that is attached to a vacuum pump may be used to draw the airout from between the glass photomask master and the resist coated mask26.

Once the glass photomask master is sufficiently positioned with respectto the substrate of the mask 26, the photoresist on the mask 26 isselectively exposed by an exposure source, e.g., using a UV lamp or maskaligner, in a manner corresponding to the pattern from the glassphotomask master. The glass photomask master is removed and thephotoresist on the mask 26 is developed, e.g., using a suitabledeveloper, to create the desired pattern in the photoresist on the mask26 corresponding to the pattern provided on the glass photomask master.After the exposure operation, a post exposure bake may be required,e.g., to complete a chemical change of the photoresist on the mask 26.After baking or other necessary treatments (if required), a developingprocess is performed, such as by spraying or otherwise washing thephotoresist from the substrate using a chemical developer solution. Ifthe photoresist is a positive resist, the portions of the photoresistthat were exposed to light from the exposure source are removed by thedeveloper. If the photoresist is a negative resist, the non-exposedphotoresist is removed from the mask 26.

A pattern forming operation is then performed at 108. For example, astandard wet etch process may be used to remove the metal, e.g.,aluminum in the present example, from the areas where there is nophotoresist. The mask substrate, e.g., the aluminized Mylar thus nowcomprises a copy of the pattern that was on the glass master with themetal remaining on the Mylar creating the opaque pattern. The copy willbe either a positive copy or a negative copy of the pattern on the glassphotomask master depending upon the resist that is used.

As yet another example, a lift-off operation may be used to form thepattern on the mask 26 at 108, which avoids the requirement of etchingpreviously deposited aluminum. Using the lift-off technique, thealuminum is not applied to the Mylar during the preparation step at 102.Rather, the photoresist is applied to the Mylar at 104 and is patternedat 106 in a manner analogous to that described above. During patternforming at 108, a layer of aluminum is applied over the patterned resistcoated Mylar and a lift-off operation is performed to remove thephotoresist and corresponding aluminum from the Mylar, leaving a patternof aluminum. For example, the mask 26 may be rinsed with a solvent thatremoves the photoresist and the excess metal that is applied to the topof the photoresist, leaving only the metal that was deposited onto theMylar in the “cleared” patterned areas of the photoresist on the mask26.

The processing requirements, the exposure source, and the size and shapeof the part to be patterned will influence the selection of maskmaterials. For example, typical parts 24 may range in size fromrelatively small, e.g., approximately one inch (approximately 2.54 cm)or smaller in at least one dimension, to relatively large, e.g., up toapproximately eight feet (approximately 2.44 m) or greater in at leastone dimension. Moreover, the feature size of the pattern is generallyindependent of the physical dimensions of the part 24, thus very largeparts may require microscopic lines patterned into the part. Stillfurther, the pattern on the mask may transparent, at least in a mannerthat is commensurate with the spectrum associated with the correspondingexposure source 27.

Scanning Exposure Methods

As noted herein, the parts to be patterned may be quite large in size,e.g., up to and exceeding 8 feet (approximately 2.44 m). As such, it maybe impractical or impossible to perform the exposure in a single step orpass. According to one aspect of the present invention, and withreference to FIGS. 3A-3D, a multi-pass exposure approach is illustratedfor creating the mask 26. As schematically shown in FIG. 3A, the system60 comprises a frame base 62 upon which the mask substrate is applied.As shown, the frame base 62 comprises a generally semi-cylindrical shapefor clarity of discussion herein. However, in practice, the frame base62 may be implemented using any suitable shape.

With reference to FIG. 3B, a film master 64, e.g., a film containing theoriginal artwork, is flexed or otherwise bent over the mask 26. Withreference to FIG. 3C, a transparent top layer 66, such as an acrylicsheet, may then applied over the film master 64. Referring to FIG. 3D,the top sheet 66, the film master 64 and mask 26 are securedsufficiently together for an exposure operation. As an example, a vacuummay be drawn, e.g., from a suitable vacuum source 68 while an exposureoperation is performed to expose the mask 26 through the film master 64and transparent top layer 66 using a suitable exposure source 70. Theexposure source 70 can be indexed about the frame base 62 in a mannerthat results in a suitable, uniform exposure of the mask 26. Forexample, the exposure source 70 may be turned on and swept in anysuitable direction so as to emit a light beam that is normal to thesurface of the mask 26 in a manner that a substantially uniform exposureis achieved.

Alternatively, the exposure source 70 may be arranged in a stationaryposition and the frame base 62 may be moved relative to the exposuresource 60. For example, the frame base 62 may be placed on a translationtable or otherwise comprise translation and/or rotational capabilitiesthat allow the frame base 62 to move relative to the exposure source 60in at least one direction. Under this arrangement, the frame base 62 isindexed to advance the mask 26 relative to the exposure source 70. Stillfurther, the exposure operation may be carried out by a combination oftranslation or other motion in both the frame base 62 and the exposuresource 70.

Referring to FIG. 4, in another exemplary implementation of the system60, the frame base 62 comprises a predetermined shape, such as acylinder, having a longitudinal axis 72 about which the frame base 62may rotate. The mask 26 is bent to conform to the outer surface of theframe base 62 in a manner analogous to that described above withreference to FIGS. 3A-D. A master film 64 having the desired artwork isapplied over the mask 26, and a top layer 66, e.g., an acrylic sheet, isprovided over the master film 64. The top sheet 66, the film master 64and mask 26 are then secured sufficiently together for an exposureoperation. As an example, a vacuum may be drawn from a suitable vacuumsource 68 to hold the mask 26, the master film 64 and the top layer 66in sufficient contact for exposure.

The exposure source 70, e.g., a UV lamp, is provided a fixed locationrelative to the frame base 62. Light 74 from the UV lamp is directedtowards a reflective device 76, e.g., a mirror, which reflects the lighttowards the surface of the frame base 62, thus exposing the mask 26. Asshown, the reflective device 76 directs the light towards the frame base62 in a direction that is generally normal to the surface of the toplayer 66. The reflective device 76 is used to index the path of the beamof light 74 from the UV source 70 to the frame base 62. As such, thesystem further includes a translation stage 78 that is provided forcausing the reflective device 76 to translate along the longitudinallength of the frame base 62. Thus, the combination of translation of thereflective device 76 along the translation stage 78, and the rotation ofthe frame base 62 about its longitudinal axis 72, allows the mask 26 tobe uniformly exposed, even where the mask 26 is relatively large.

The system 60, as illustrated with reference to FIGS. 3A-3D; and 4 maybe useful, for example, where flood exposure is unsatisfactory due tothe particular circumstances of the application, e.g., size of themask/part etc. Also, by translating at least one of the exposure source70 (or corresponding reflective device 76 and translation stage 78), orby moving the frame base 62, a uniform exposure light coverage can berealized by maintaining the beam 74 emitted from the exposure source 70substantially normal to the surface of the mask 26. However, stillfurther arrangements can be implemented within the spirit of the presentinvention that provide for selective exposure. For example, a laserdirect-write method can be used, e.g., by utilizing an appropriatemulti-axis gantry and by using a laser to direct-write the pattern intothe photoresist applied to the mask 26.

As noted above, other materials in addition to, or in lieu of,aluminized Mylar may be used to form the mask 26. The particularmaterial should be selected so as to be capable of surviving theparticular processing conditions. For example, the mask 26 should beable to be deformable (elastically or in-elastically) within therequirements of the part 24 to be patterned. More particularly, the masksubstrate may be stretched in certain applications from approximately5%, up to and exceeding 100% of the size of the non-stretched masksubstrate material. The amount of required stretching may affect theselection of mask substrate materials.

During use, it may be desirable to deform the mask 26 so as to notexceed the elastic limits of the mask substrate. However, the masks 26created as set out herein may be re-used, even if a mask 26 is deformedpast its elastic limits. For example, there may be enough elasticityleft in the material to deal with part-to-part variations. Part to partvariation is compensated for because each use of the mask 26 allows themask 26 to adapt and conform to the part 24 so as to compensate for partvariances in dimensions.

Moreover, the selected material(s) utilized to construct the mask 26should be able to be patterned to include opaque portions that block thelight from the corresponding exposing light source, and transparentportions that allow light from the exposing light source to passthrough. However, the opaque layer does not require a metal layer.Rather, paint, varnish or other coatings may be applied. Under thisarrangement, the pattern in the mask 26 may be formed using laserablation or other suitable fabricating techniques. Moreover, a suitablemask 26 may be formed using the techniques as set out in greater detailin U.S. Provisional Application Ser. No. 60/822,134 filed Aug. 11, 2006,entitled “PATTERNING COMPOSITIONS, MASKS AND METHODS”, which isincorporated by reference herein.

When preparing the mask 26, compensation to the artwork may also beuseful to pattern the mask 26 in such a way as to account for linewidths and line spacing when the mask 26 is deformed. For example, amask 26 may be physically capable of conforming to a corresponding part24, e.g., by recessing into the deep dimple in the non-planar area 24Aof the part 24 shown in FIG. 1. However, such drastic stretching mayaffect the line widths of the pattern such that the lines are no longerwithin a predetermined tolerance as may be required by a specificapplication. As such, by altering the artwork applied to the mask 26 aspart of the patterning process, some or all of the error may becompensated for so that as the mask 26 is deformed, the changes to thepattern do not fall outside of a predetermined specification. Thespecific application and the required precision of the pattern appliedto the part 24 will likely determine the manner in which the artwork isprepared.

At the end of the method 100 described with reference to FIG. 2, themask 26 may remain in its default shape, e.g., a substantially flatsheet, or the mask 26 may be in some other shape. For example, there maybe some amount of stretching or deformation of the mask 26 as a resultof mask processing, e.g., as a result of being flexed around the framebase 62 during mask patterning, etc. Shaping of the mask 26 as a part ofmask processing need not require that the shape of the mask 26 conformto the shape of intended corresponding part 24 during mask patterning.As noted above, the mask 26 may be wrapped about a cylinder, or take onother shapes as necessary to facilitate processing.

Alternatively, the mask 26 may have been processed in a substantiallyflat state, or the elastic limits of the mask 26 may not have beenexceeded by the pre-pattern processing. Thus, after the pattern isformed at 108, the mask 26 may return to (or remain in) its defaultshape, e.g., a substantially flat sheet, or the mask 26 may retain someother shape. Regardless, the mask 26 will be deformed during processingof the part 24 as will be described below. This allows the mask 26 toaccommodate non-planar surfaces on a given part 24 to be patterned, toaccommodate part to part variations between instances of parts 24 duringprocessing and/or to allow the tolerance in the part itself to be openedup, if the specific application allows for such. The deformation of themask 26 for patterning a part, such as by using the system 10 orvariations thereof, will be described in greater detail herein.

Patterning A Part

With reference to FIG. 5, a method 120 is illustrated, for patterning apart having a non-planar surface, e.g., using the system 10 shown inFIG. 1. For sake of illustration, the part 24 is shown as having anon-planar surface area 24A comprising a relatively deep dimple thatincludes sharp changes of the surface contour of the part 24 along theperimeter of the dimple. The dimple geometry should not be considered aslimiting to the various aspects of the present invention, but rather, isshown to demonstrate that various aspects of the present invention canbe utilized to deform a mask 26, e.g., a generally flat substrate asshown, so as to correspond to parts that include complex curves, steepand/or sharp changes in surface contour and other complexconfigurations.

Initially, a mask 26 is prepared at 122. The activities performed toprepare the mask at 122 may be analogous to those described at 102 toprepare a mask substrate as described with reference to the method 100shown in FIG. 2. Additionally, a part 24 is coated with photoresist at124, e.g., using a conventional spin or spray coat process.

At 126, the part 24 having the photoresist coat thereon is placed in thechamber base 12, such as by setting or otherwise securing the part 24 tothe platform 18. At 128, the mask 26 is secured in the mask retainer 16so as to orient the mask 26 proximate to the part 24 toward thephotoresist. When the mask 26 is placed in the mask retainer 16, themask substrate may be optionally stretched in one or more directions. Inthis regard, the mask 26 may be substantially flat, or the mask 26 mayhave some shape that is not substantially flat. However, the mask 26 istypically not shaped to conform to the part 24 at this time. At 130, thepressure vessel 14 is attached to the chamber base 12 and/or retainerdevice 16, and at 132, the pressure sources 20 are utilized within thechamber so as to deform the mask 26 to the shape of the part 24,including any non-planar surface(s) 24A. Also at 132 (or some otherappropriate step), the mask 26 may be aligned to the part 24.

Referring to FIG. 6, assume the mask 26 comprises a suitably deformablemask substrate, e.g., an aluminized Mylar mask, and the part 24 includesa non-planar surface area 24A having a dimple there-along asschematically represented in the illustration of an exemplary part asshown. In the illustrated arrangement, the mask 26 and/or mask 26 incooperation with the retaining device 16, spans a cross-section of thechamber. As such, the mask 26 in cooperation with the retaining device16 separates the pressure vessel space within the chamber from thechamber base space within the chamber.

As noted above with regard to the discussion of FIG. 1, the first andthird pressure sources 20A, 20C may each comprise a vacuum source andthe second pressure source 20B may comprise a positive pressure sourcesuch as compressed nitrogen. Initially, the first control valve 30 maybe opened sufficient to allow the first pressure source 20A to begindrawing a vacuum from the bottom of the chamber. Also, the third controlvalve 46 may be opened to allow the third pressure source 20C to begindrawing a vacuum from the top of the chamber. As such, the pressurevessel space defines an upper vacuum space and the chamber base space,which contains the part 24, defines a lower vacuum space.

As a vacuum is drawn from both the top and bottom of the mask 26, thepressure may be insufficient to cause the mask 26 to deform to a mannersubstantially conformal to the part 24. However, drawing a vacuum fromboth the top and bottom may allow the mask 26 to be aligned, and gasthat is trapped between the part 24 and the mask 26 may be evacuated.

As another example, a vacuum may be drawn first in the pressure vesselspace, e.g., using the third pressure source 20C. Subsequently, a vacuummay be drawn in the chamber base space below the mask, e.g., using thefirst pressure source 20A. Next, the pressure vessel space may bevented, such as by closing the third control valve 46 and by temporarilyopening the second relief valve 46. The mask 26 can then be pushed orotherwise positioned with respect to the part 24 without trapping airtherebetween.

There are a number of approaches to utilizing the pressure sources 20 todeform the mask 26, such as by creating a pressure differential withinthe chamber. For example, after drawing trapped air and/or suitablyaligning the mask 26 over the part 24, the second control valve 40 maybe opened, allowing the second pressure source 20B to exert a positivepressure on the mask 26 while a vacuum is maintained in the chamber basespace.

Thus, the pressure vessel space may be transformed from the upper vacuumspace, to a positive pressure space. The positive pressure on thepressure vessel side of the chamber, and the negative pressure/vacuum onthe chamber base side of the chamber will thus cause the mask 26 todeform towards the shape of the part 26. In this regard, the pressureapplied by either the first or second pressure sources 20A, 20B may bevaried. For example, the first pressure source 20A may be set to a firstvalue when aligning the mask 26 and removing gas from between the part24 and mask 26, and the first pressure source 20A may be operated at adifferent pressure for deforming the mask 26.

Still further, one or more of the pressure levels may be periodicallyand/or continuously adjusted during the exposure operation. For example,the pressure within the chamber may not be sufficient to bring the Mylarmask 26 into intimate contact with the part 24, including the non-planarsurface area 24A, e.g., in the “dimple” region as schematicallyillustrated, when the second pressure source 20B is initially applied.Thus, a pressure from the nitrogen source 20B may be maintained orgradually increased over a period of time to generate a sufficientlyhigh pressure from the vessel side of the mask 26. As nitrogen isintroduced into the vessel 14, the Mylar mask 26 will continue todeform, e.g., by stretching down into the dimple in the example.Similarly, the pressure from the vacuum of the first pressure source 20Amay be maintained or gradually increased over a period of time togenerate a sufficient pressure from the chamber base side of the mask26. Thus, both the first and second pressure sources 20A, 20B eachperform the functions of drawing the mask 26 towards the part 24 anddeforming the mask 26 to conform to the part 24. The time to achievecontact will vary depending on factors such as the geometry of the part,the ability of the mask 26 to deform, etc.

When there is sufficient contact between the part 24 and the mask 26,there may be a visible difference between the areas with good contactand no contact. For example, in one exemplary arrangement, an aluminizedMylar mask was used to pattern a part having a dimple. As completecontact between the part 24 and the Mylar mask 26 approached, fringepatterns were visually detected that became increasingly visible.

In the example described above with reference to FIGS. 5 and 6, thefirst, second and third pressure sources 20A, 20B, 20C are utilized in asuitable combination, e.g., using differential pressure to deform themask 26 to substantially conform to the part 24, including thenon-planar surface area 24A. Depending upon the mask material, thetemperature of the system 10 may also be controlled, monitored orotherwise maintained within predetermined target range(s) by atemperature control system 52, e.g., to assist in the deformation of themask 26 to conform to the part 24, or to establish conditions in whichthe mask material is deformable. For example, a photosensitive maskmaterial may deform at temperatures of less than about 50° C., which maybe desirable, for example, where the part 24 cannot be exposed toelevated temperatures. Alternatively, the mask 26 and/or the system 10may be heated to assist in deforming the mask 26 to the part 24. Assuch, FIG. 6 schematically shows that the mask 26 has recessed down intothe non-planar surface area 24A, i.e., the dimple as shown, of part 24.

With reference to FIGS. 5 and 6, once suitable deformation of the mask26 is achieved relative to the part 24, an exposure operation isperformed at 134 while the mask 26 is held in a deformed state, e.g., ina state that is substantially conformed to the shape of the part 24 asshown. Keeping with the above example, once the Mylar mask 26 is insufficiently complete contact with the surface of the part 24, which maybe determined for example, based upon the precision and required featuresize of the pattern, the setup is ready for exposure. To expose thephotoresist through the deformed mask 26, the system 10 is positionedsuch that the pressure vessel 14 is under the UV lamp. When determiningexposure times, it may be necessary to account for factors such as theattenuation of the light as a result of the material of the pressurevessel 14, which may filter the UV light. During the exposure, both thefirst and second pressure source 20A, 20B may remain on to ensure thatmaximum contact between the part 24 and the mask 26 is maintained.

After exposure, pressure sources 20 are relieved at 136, e.g., using thefirst relief control valve 32 and first relief passageways 34, and/orthe second relief control valve 46 and second relief passageway 48. Thepart 24 is then removed from the chamber base 12 at 138, e.g., afterpressure in both the chamber base 12 and the vessel 14 are returned toatmosphere. A development process is performed at 140 to remove thephotoresist in one of the exposed or unexposed regions of thephotoresist, e.g., using conventional techniques. For example, the part24 may be baked during a post exposure bake. Once the part 24 has been(optionally) baked and is cool, the part 24 may be developed. Stillfurther, depending upon the nature of the part 24, it may be necessaryto perform a post pattern inspection, e.g., to detect whether there areregions where the resist has not totally developed away and/or to detectwhether there are areas of very small cracks in the opaque layer of themask that were imaged onto the lines, etc. Such types of potentialproblems may be taken care of by additional developing, e.g., with ahigher concentration developer applied only in the areas that requirethe additional developing. Once developed, additional processing stepsmay be performed as the specific application dictates.

The necessary processing for completing the part 24 is then performed at142. For example, if a conductive pattern is to be applied to the part24 via a lift off technique, the part 24 is then coated with aconductive layer, e.g., by conformally coating the part 24 with aconductive material. Where the photoresist has been removed, theconductive material will contact the part 24. Alternatively, theconductive layer will form above the photoresist that remains on thepart 24. Depending on the uniformity requirements and the geometry ofthe part, tooling and rotation schemes may needed to suitably coat thepart.

A lift off operation is then performed to remove the remainingphotoresist from the part 24, and hence the conductive material on thephotoresist. When the part 24 is conformally coated with the conductivematerial, a thin steep wall of conductive material will form between thelayer of conductive material on the photoresist and the layer ofconductive material on the surface of the part 24. When the photoresistis removed, e.g., by spraying or submerging the part with a suitablesolvent solution, the thin, steep walls of conductive material willbreak, releasing the remaining photoresist and corresponding conductivematerial that was layered over the photoresist. However, the conductivematerial applied to the surface of the part 24 remains adhered to thepart 24.

As an alternative to the lift off technique, an etch process may beutilized, e.g., by applying a conductive coating to the part 24 beforeapplying the photoresist to the part 24 at 124. In this example, afterdeveloping the photoresist, a conventional etch process may be utilizedto etch away the conductive material exposed after developing thephotoresist.

As yet a further example, the processing at 142 may comprise any type oftreatment that could be selectively applied to the substratecorresponding to the photoresist pattern. This process could include wetetching such as with HF or dry etching such as RIE or a process like ionimplantation where the substrate is modified by the addition of othermaterials into the substrate. If the photoresist was opaque enough to UVlight, the sample could be hydrogen loaded and exposed with UV light tomodify the index of refraction forming a waveguide as an example. Thus,subsequent operations involving metal pattern formation is not required.

It may be necessary to remove trapped air bubbles between the part 24and the mask 26. According to an aspect of the present invention, someair bubbles may be eliminated between the part 24 and the mask 26 beforeperforming the exposure operation by pushing air from the center to theedges and out of the contact area, e.g., using standard laminatingtechniques. Once the air bubbles are suitably removed from between thepart 24 and the mask 26, the first and second vacuum sources 20A and 20B(or some other combination of pressure sources 20) may be used to deformthe mask 26 according to the part 24 in the chamber.

In an illustrative example, the area above the mask 26, e.g., thepressure vessel space, may be first evacuated to define a negativepressure space and then the air below the mask 26, e.g., the chamberbase space, may be evacuated. Next, the pressure vessel space above themask 26 may be vented. As such, the mask 26 can be pushed around forpositioning and alignment without trapping air between the part 24 andthe mask 26.

As yet another illustrative example, a vacuum may be applied to both thechamber base 12 and the vessel 14 more or less simultaneously to preventdeformation of the mask until the mask 26 is suitably aligned with thepart 24 as described more fully above. Once the mask 26 is aligned tothe part 24, the two vacuum sources, e.g., pressure sources 20A and 20Ccan be utilized to create a pressure differential sufficient to deformthe mask 26 to conform to the part 24. As yet another example, thepressure vessel space can be evacuated and replaced with a positivepressure, as described more fully herein.

Mechanical Approaches to Aid in Deforming the Mask for Patterning a Part

Pre-shaping of the mask 26 may be useful, such as to reduce the timerequired to deform the mask 26 in the system 10 and/or to complete therequired deformation of the mask 26. The mask 26 may be mechanicallydeformed after the mask 26 has been patterned and before and/or duringuse of the mask 26 in patterning a part 24.

Referring to FIG. 7, a method 150 illustrates yet another exemplarymethod of performing an exposure operation for a part having anon-planar surface area. A mask 26 having a desired pattern thereon isdeformed at 152. The mask is associated with a part to be exposed at 154and a vacuum is pulled between the mask and the part at 156. Afterpulling the vacuum, the method may optionally bleed the space adjacentto the mask and opposite of the part 24 to atmosphere at 158. Forexample, where using a system such as that described with reference toFIGS. 1 and 5, the pressure vessel space may be evacuated to draw themask to a corresponding mold to deform the mask 26. Once the mask 26 issuitably mated with the part 24, the system may bleed the pressurevessel space. The part 24 is then exposed at 160 through the mask 26.

The optional step at 158 to bleed the space adjacent to the mask 26 toatmosphere provides flexibility in the manner in which the exposure at160 is implemented. For example, when using a two part chamber, such asthat described with reference to FIG. 1, after bleeding the spaceadjacent to atmosphere, the pressure vessel 14 can be removed from thechamber base.

Referring to FIG. 8, the system 10 may be used to perform the methoddescribe in FIG. 7. As shown, a mold 54 is provided in the pressurevessel 14 above the mask 26. In a first state, system 10 comprises thedeformable mask 26 secured to the retaining device 16, which is coupledto the pressure vessel 14. The chamber base 12 may be optionally securedto the pressure vessel 14 and/or retaining device 16. A vacuum ispulled, e.g., using the third pressure source 20C, to deform the maskupward against the mold. For example, as noted above, the mask 26 and/ormask 26 in cooperation with the retaining ring 16 divide the chamberspace into a pressure vessel side and a chamber base space. By pulling avacuum in the pressure vessel space (or upper vacuum space in the systemas illustrated), the mask 26 can be deformed to the shape of the mold54. In this regard, the mold 54 may take a shape that is complimentaryto the desired non-planar surface area 24A of the part 24, or the mold54 can take some other shape.

If necessary, the chamber base 12 is mated with the pressure vessel 14,the mask 26 is brought down in cooperation with the part 26 to beexposed and a vacuum is pulled between the mask 26 and the part 24,e.g., using the first pressure source 20A. When a sufficient vacuum hasbeen pulled, the second relief control valve 46 may be opened to bleedthe pressure vessel 14 to atmosphere. Thus, the system bleeds atmosphereinto the upper vacuum space above the mask 26. However, the vacuum drawnbetween the part 24 and the mask 26 remains so that the mask is deformedto the part 24, including a non-planar surface of the part 24.

Referring to FIG. 9, under these conditions, it may now be possibleorient the system 10 to a second state, wherein the pressure vessel 14is removed from the chamber base 12. The mold 54 may also be removedfrom association with the mask 26. Alternatively, the mold 54 mayremain, such as where the mold is transmissive to the light from theexposure source 27. As such, an exposure operation may be performed byexposing the part 24 through the mask 26, such a by using a suitable UVexposure source 27. In this regard, the exposure source 27 does not haveexpose the part through a window or other suitable portion 14A of thepressure vessel 14. As noted in the discussion with reference to FIGS. 8and 9, the pressure sources 20 need not be operated simultaneously tocreate a differential pressure. Rather, the pressure sources 20 mayalternatively be operated in a sequential manner.

As another example, a mechanical force may be used as an alternative toand/or to assist the pressure created in the chamber of the system 10,e.g., to reduce the required pressure to deform the mask 26 so as thatthe mask 26 achieves sufficient intimate contact with the part 24 forexposure.

Referring to FIG. 10, a mechanical backing device 96, e.g., a moldablefoam or other suitable material or composite, is utilized to applymechanical pressure to the mask 26 so as to achieve (or assist inachieving) intimate contact between the part 24 and the mask 26. In theillustrated example, the mask 26 is essentially sandwiched between thepart 24 and the backing device 96. As shown, the backing device 96 isdimensioned to correspond to the dimple (or any other suitablenon-planar surface 24A of the part 24). The backing device 96 mayconform to the shape of the part 24 or the non-planar surface area 24Aof the part 24, or the backing device may have a simple or complex shapethat is different from the part 24 or the non-planar surface area 24A ofthe part 24. Regardless, the backing device 96 essentially applies amechanical force to assist in the deformation of the mask 26. Thebacking device may be transmissive to light from the exposure source 27,e.g., if the backing device 96 remains in the chamber during exposure.

Referring to FIG. 11, the system need not position the mask 26 abovepart 24 as shown in FIG. 1. For example, an exposure operation may beperformed from the bottom of a suitable chamber utilizing the system200. As shown, a chamber comprises a chamber base 202 on a top portionof the chamber and a pressure vessel 204 on a bottom portion of thechamber. A retaining device 206 is utilized to secure the mask 26 withinthe chamber of the system 200. The part 24 is secured to a platform 208and is situated just above the mask 26, which is held by the retainingdevice 206. The part 24 is positioned within the chamber so that anon-planar surface area 24A, e.g., a convex surface profile, is directedtowards the mask 26. The pressure sources 20 are then operated to bringthe mask 26 into contact with the part 24 sufficient for exposure. Forexample, as noted in greater detail above, a pressure differential maybe applied by two or more pressure sources 20 to bring the mask 26 intocontact with the part 24 sufficient for exposure.

Further, a mechanical device, such as the optional backing device 96 maybe positioned under the mask 26, e.g., so as to press the mask 26 upagainst the part 24 and/or to provide suitable support to the part 24.Once the appropriate pressure(s) have been established by the pressuresource(s) 20, the backing device 96 may be left in place, e.g., wherethe backing device 96 is transmissive the exposure source 27, or thebacking device 96 may be removed, e.g., after a vacuum has been drawnand the mask 26 is sufficiently conformal to the part 24.

Referring to FIG. 12, another exemplary system 300 is illustrated, thatutilizes mechanical deformation of the mask 26. The mask 26 may bepatterned as a substantially flat sheet, e.g., using the techniquesdescribed above. In this example, the flexible sheet defining the masksubstrate is held by a pair of plates 302 and is heated by a temperaturecontrol 304 while a desired shape 306, e.g., a copy of the part 24, aspherical object or other object having any desired shape, is pressedinto the sheet. The system 300 may be separate from the system 10 usedto pattern the part 24. Alternatively, the system 300 may be integratedinto the system 10, e.g., using the retaining device 16 to function asthe plates 302. The patterned flexible material forms to the desiredshape by stretching or a combination of shrinking and stretching. Theheat is removed and the sheet is allowed to cool while still being heldin position. In this context, the desired shape may comprise a basicshape, or a more complex shape, e.g., an approximation of thecorresponding part 24 to be patterned.

Referring to FIG. 13, the previously patterned mask 26 may alternativelybe mechanically deformed using a molding system 310. The mask 26, isplaced, e.g., while in a flat or substantially flat shape, within a mold312, e.g., consisting of first and second complimentary blocks as shown.The mask 26 may be deformed by a combination of stretching and/orshrinking while in the mold. Further, the deformation of the shape ofthe mask 26 may be assisted while in the molding system 310, usingtemperature control 304, a chemical treatment or other suitableaccelerant. In this context, the desired shape of the mold 312 maycomprise a basic shape, or a more complex shape, e.g., an approximationof the corresponding part 24 to be patterned. Other shaping techniquesmay alternatively be used.

Using the Part as the Mask

Referring to FIG. 14, under certain circumstances, it may be possible toform the part so that the part itself is the mask 26. For example, apart 24 is coated with a layer of photoresist 98. The part 24 isinfiltrated or otherwise treated, e.g., using photodarkening techniques,varnish, paint or other suitable treatments that coat or otherwisepenetrate the part substrate in a manner such that the pattern ispermeated through the part thus defining areas of the part itself thatare transmissive to the exposure source 27, and areas that are nottransmissive to the exposure source 27. As some examples, the partsubstrate may be transmissive to light from the exposure source. Assuch, a paint, varnish or other opaque material may be applied to thesurface of the part to define areas that are non-transmissive to theexposure source. As another example, a substrate of the part may betransmissive to the exposure source except where the substrate isinfiltrated with a treatment that renders the infiltrated areasnon-transmissive to the exposure source. As yet a further example, thepart substrate may be non-transmissive to the exposure source exceptwhere the substrate is infiltrated with a treatment that renders theinfiltrated areas transmissive to the exposure source 27.

As an example, the various techniques described in U.S. ProvisionalApplication Ser. No. 60/822,134 filed Aug. 11, 2006, entitled“PATTERNING COMPOSITIONS, MASKS AND METHODS” may be utilized to fashionthe mask 26 integral with the part 24 itself. The exposure source 27 isthen used to expose the photoresist 98 through the part 24 withoutrequiring a separate, detached deformable mask 26. After exposure, adevelopment operation is performed to remove portions of the photoresist98 and any desired subsequent processing of the part 24 may beperformed.

Gas Permeable Mask

In the design of a deformable (or even flexible or rigid) mask 26, itmay be difficult to obtain sufficiently intimate contact with thecorresponding part 24 in the non-planar surface area 24A of the part 24.For example, when the mask 26 is aligned over the part 24, there is arisk of trapping air and corrupting intimate contact in local regions inthe contact area between the part 24 and the mask 26, thus affecting thequality of the exposure.

In certain applications, trapped air is difficult to avoid. However, itmay be unacceptable due to manufacturing constraints, e.g., featuresize, to allow the air bubbles to remain. According to one aspect of thepresent invention, the mask 26 is constructed from a substrate materialthat is gas permeable so that intimate contact with the final part 24may be facilitated by providing a means for the air bubbles to escape.

As an example, the mask 26 may comprise a polymer. Thus, any gas, suchas helium, that is permeable to the polymer may be used in the system10. According to an aspect of the present invention, helium is used asan intentional atmosphere during contact lithography. Helium is arelatively small molecule that is readily available. If the contactregion between part 24 and the mask 26 is purged of other gases and issubstantially filled with helium, then any trapped gas would be able topermeate the polymer mask 26. Thus, evacuating the area between the part24 and the mask 26 may not be entirely necessary if the region cansimple be purged with helium or another permeable gas. Moreover, thiseliminates the potential for errors in the standard laminationtechniques to minimize trapped air where a gas is used that can permeatethe mask 26. The gas permeable mask 26 may be used, for example, withthe assistance of a mechanical backing device 96, and/or with othertechniques and systems such as those described more fully herein.

The present invention is described below with reference to flowchartillustrations and/or block diagrams of methods and apparatus (systems).It will be understood that each block of the flowchart illustrationsand/or block diagrams, and combinations of blocks in the flowchartillustrations and/or block diagrams may be implemented and/or controlledby computer program instructions. For example, a computer may be used tocontrol exposure times, to control the pressure sources 20, includingthe relief valves, etc., to control automation of devices such as thetranslation stage 78 described with reference to FIG. 4, etc. Thesecomputer program instructions may be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems and methods according to various embodiments of the presentinvention. In this regard, the functions noted in the block may occurout of the order noted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Having thus described the invention of the present application in detailand by reference to preferred embodiments thereof, it will be apparentthat modifications and variations are possible without departing fromthe scope of the invention defined in the appended claims.

1. A method of forming a pattern on a complex non-planar surface of apart comprising: forming a layer of photoresist on a part having asurface comprising a complex non-planar surface area; positioning saidpart within a chamber defined by a chamber base and a pressure vesselsuch that said part is positioned within said chamber base, wherein afirst pressure source is coupled to said chamber base and a secondpressure source is coupled to said pressure vessel; securing adeformable mask in a retaining device between said chamber base and saidpressure vessel so as to align said deformable mask towards saidphotoresist on said part and divide said chamber into a pressure vesselspace above said mask and a chamber base space below said mask; drawinga first vacuum in said chamber base space using said first pressuresource; applying a positive pressure in said pressure vessel space usingsaid second pressure source to deform said mask to correspondsubstantially to said part including said complex non-planar surfacearea; exposing said photoresist on said part through said mask aftersaid mask deforms to correspond to said part including said complexnon-planar surface area; removing said part from said chamber; anddeveloping said photoresist on said part.
 2. The method according toclaim 1, wherein a third pressure source is coupled to said pressurevessel, further comprising: drawing a second vacuum in said pressurevessel space using said third pressure source before drawing said firstvacuum in said chamber base space; venting said pressure vessel spacewhile maintaining the vacuum in said chamber base space; and performingat least one of evacuating gas trapped between said part and said maskand repositioning said mask relative to said part.
 3. The methodaccording to claim 1, wherein a third pressure source is coupled to saidpressure vessel, further comprising: drawing a second vacuum in saidpressure vessel space using said third pressure source substantiallysimultaneously with drawing said first vacuum in said chamber base spaceto prevent deformation of said mask; and performing at least one ofevacuating gas trapped between said part and said mask and repositioningsaid mask relative to said part.
 4. The method according to claim 1,wherein said applying a positive pressure in said pressure vessel spacecomprises: applying said positive pressure simultaneously with drawingsaid first vacuum in said chamber base space to create a differentialpressure to deform said mask to correspond substantially to said partincluding said complex non-planar surface area.
 5. The method accordingto claim 1, wherein said applying a positive pressure in said pressurevessel comprises: deforming said mask within a range corresponding tothe elastic limits of said deformable mask such that said deformablemask returns generally to a first shape upon removal of said first andsecond pressure sources, said first shape not conformal to saidnon-planar surface area of said part.
 6. The method according to claim1, further comprising pre-shaping said mask using a mechanical backingdevice to temporarily deform said mask within said chamber.
 7. Themethod according to claim 6, wherein said exposing said photoresist onsaid part further comprises exposing said part through said mask andsaid mechanical backing device.
 8. The method according to claim 1,further comprising selecting said mask to have a substrate that ispermeable to a gas used for atmosphere when exposing said photoresist.9. A method of forming a pattern on a complex non-planar surface of apart comprising: deforming a mask against a mold; bringing said maskinto cooperation with a part to be patterned while said mask is deformedagainst said mold, wherein said part has at least one complex non-planarsurface area coated with a photoresist layer; pulling a vacuum betweensaid mask and said part such that said mask deforms to said partincluding said at least one complex non-planar surface area; removingsaid mold from said mask so that said mask remains deformed to saidpart; exposing said part through said mask; and developing said part.10. The method according to claim 9, further comprising installing saiddeformable mask in a pressure vessel, wherein: said deforming a maskagainst a mold comprises drawing a vacuum between said mask and saidmold in said pressure vessel to define an upper vacuum space.
 11. Themethod according to claim 10, further comprising installing said part ina chamber base, and coupling the pressure vessel to the chamber base,wherein said pulling a vacuum between said mask and said part such thatsaid mask deforms to said part including said at least one non-planarsurface area comprises pulling said vacuum in said chamber base so as topull said mask to said part.
 12. The method according to claim 11,further comprising: bleeding atmosphere into said upper vacuum spacesuch that said mask remains deformed against said part; and uncouplingsaid pressure vessel from said chamber base such that said mask remainsdeformed against said part, wherein said exposing said part through saidmask comprises exposing said part without interference of said pressurevessel.
 13. The method according to claim 12, further comprising:removing said mold before exposing said part.
 14. A method of making adeformable mask for contact lithography comprising: applying photoresistover a deformable mask substrate; shaping said mask substrate to a firstpredetermined shape by wrapping said mask substrate about a frame;applying a master having desired artwork thereon over said photoresiston said deformable mask substrate; exposing said photoresist using anexposure source to define a desired pattern while said deformable maskis in said first predetermined shape; and forming said pattern in saidphotoresist by removing portions of said photoresist corresponding to adesired pattern, wherein said deformable mask does not retain a shapecorresponding to a part having a complex non-planar surface area to bepatterned by said deformable mask when in a default state, but doesdeform to correspond substantially to said part including said complexnon-planar surface area during patterning said part.
 15. The methodaccording to claim 14, wherein said exposing said photoresist using anexposure source to define a desired pattern comprises: indexing at leastone of said frame or said exposure source such that said photoresist issubstantially uniformly exposed.
 16. The method according to claim 15,wherein said indexing at least one of said frame or said exposure sourcesuch that said photoresist is substantially uniformly exposed comprises:positioning an exposure device in a fixed location; directing a lightbeam emitted from said exposure device to a reflective device; andtranslating said reflective device so as to substantially uniformlyexpose said photoresist.
 17. The method according to claim 15, whereinsaid indexing at least one of said frame or said exposure source suchthat said photoresist is substantially uniformly exposed comprises:positioning an exposure device in a fixed location; directing a lightbeam emitted from said exposure device to a reflective device;translating said reflective device in a longitudinal direction; androtating said frame about said longitudinal axis.
 18. The methodaccording to claim 14, further comprising drawing a vacuum to securesaid mask substrate and said master to said frame.